Stability of pesticides stored on polymeric solid-phase extraction cartridges

The stability of four pesticides (desethylatrazine, fenamiphos, fenitrothion and fonofos) was examined under different storage conditions after preconcentration in disposable solid-phase extraction (SPE) cartridges containing new polymer sorbent materials (Hysphere-1, IST EnviroLut and LiChrolut). Complete recovery for all the compounds was observed in precolumns kept at -20 degrees C for 1 month when preconcentrating 26 ml of ground water sample spiked at 10 mu g/l. Degradation of fenamiphos and fenitrothion occurred in precolumns stored at 4 degrees C and at room temperature after 1 month. Fonofos was stable when compared to their storage in C-18 precolumns. Problems in the quantification of the analytes after storage at 4 degrees C and at room temperature were encountered due to the presence of many interfering peaks in the chromatograms. Analysis of blanks with C-18 precolumns was carried out, to determine the interferences. The stability of the pesticides was also examined in acidifed and non-acidified ground water in order to compare it to the stability of pesticides stored on SPE cartridges. Significant losses of fenamiphos and fenitrothion were achieved and were related to the pH of the water sample and their chemical structure. Finally, the new polymeric sorbent Hysphere-1 was evaluated in terms of breakthroughs and compared with those of C-18, obtaining higher recoveries for desethylatrazine. (C) 1997 Elsevier Science B.V.